The purpose of this project is threefold: 1) to identify "addict" smokers, i.e., those who experience withdrawal from nicotine per se, 2) to define the nature, course and duration of withdrawal symptoms and to isolate these connected with primary reinforcement (nicotine) from those associated with habit cessation and 3) to determine experimentally the efficacy of nicotine gum in a replacement-extinction procedure where smokers are "weaned" off nicotine while they cold turkey the secondary reinforcing components of the habit. In the current study, subjects are given physiological and psychological baseline tests before quitting and then are followed daily during cessation while on one of the two gums - placebo gum or nicotine gum. "Clinic" support is offerred to each subject while undergoing testing and during all follow-up phases. In a second study, two groups will be added to the present conditions which will receive either placebo or nicotine gum but will not receive "clinic" support. This will be done to determine the role of such support systems in the comparisons of these two gums. Questionnaires will continue to be tested (for predictive efficacy) and refined in a systematic way with the goal of producing a brief questionnaire that can distinguish among smoker "types". Specifically, one which allow us to identify the smoker who is most likely to smoke for nicotine and continue to avoid withdrawal.